You need to get it from the following link at SR Researchs support forum - account required:
The eyelink_core.framework is the minimum needed for Psychtoolbox Eyelink() mex file to work.
Wrt. to the Screen() failure you encountered with PTB 3.0.17, so far all we know is that it is yet another bug in Apples shoddy macOS operating system, problem under investigation in this thread:
One workaround that may or may not work for the time being with PTB 3.0.17 is adding:
Screen(‘Preference’,‘ConserveVRAM’, 512); to the top of a script. PTB 3.0.16 is unsupported since a months, so you would be on your own if you encountered further problems with it.
-mario